The standardization of an image coding scheme called HEVC (High Efficiency Video Coding) by JCTVC (Joint Collaboration Team-Video Coding), which is a joint standardization organization of ITU-T and ISO/IEC, is currently under way for the purpose of improving coding efficiency more than H. 264/AVC (see, for example, Non-Patent Literature 1 below).
HEVC provides not only coding of a single layer but also scalable video coding, as in known image coding schemes such as MPEG2 and AVC (Advanced Video Coding). An HEVC scalable video coding technology is also called SHVC (Scalable HEVC) (for example, see Non-Patent Literature 2 below).
Incidentally, scalable video coding is generally a technology that hierarchically encodes a layer transmitting a rough image signal and a layer transmitting a fine image signal. Typical attributes hierarchized in the scalable video coding mainly include the following three:                Space scalability: Spatial resolutions or image sizes are hierarchized.        Time scalability: Frame rates are hierarchized.        SNR (Signal to Noise Ratio) scalability: SN ratios are hierarchized.        
Further, though not yet adopted in the standard, the bit depth scalability and chroma format scalability are also discussed.
In Non-Patent Literature 3, color gamut scalability in which color gamuts are hierarchized is discussed. For example, in high definition (HD) televisions, an image size of 1920×1080 pixels, a color gamut of ITU-R BT.709, and a bit depth of 8 bits are generally used. On the other hand, in ultra high definition (UHD) televisions, use of an image size of 4000×2000 pixels or 8000×4000 pixels, a color gamut of ITU-R BT.2020, and a bit depth of 10 or 12 bits is being investigated. In general, for conversion of a color gamut, it is necessary to perform matrix calculation on 3-dimensional pixel vectors. However, from the viewpoint of approximating a relation between BT.709 and BT.2020 to a linear relation independent for each color component, Non-Patent Literature 3 proposes predicting a pixel value of an enhancement layer from a pixel value of a base layer by a simple method when BT.709 is used in the base layer and BT.2020 is used in the enhancement layer.